Corn tortillas are made from water and fresh masa (nixtamal) or from the dried, ground version of masa called masa harina. Starting with yellow or blue corn the kernels are treated with slaked lime (calcium hydroxide), an alkalinization process that removes the whole corn's tough outer hull and significantly improves the nutritional profile of the grain. It also provides that distinctive, slightly sour flavor that one expects from corn tortillas.
The mixture is rolled into a ball and flattened into a circle either by hand or with a special tortilla press. Both sides are briefly cooked on a hot griddle. Corn tortillas can also be deep-fried to make them crisp and retain certain shapes. Both tostada and chalupa shells are flat while taco shells are made into a U-shaped form.
Simple corn tortillas free of additives are generally easy to find. They are at their best when freshly made but well-made brands can taste good when reheated.
Avoid those made with artificial colors or with preservatives and acidulants such as calcium propionate, potassium sorbate, sorbic acid, fumaric acid. Although safe as ingredients, the addition of gum arabic, a plant exudate from the Anogeissus latifolia tree, as well as cellulose gum are unnecessary. While gums can help keep the tortillas from falling apart, fresh tortillas that are stored properly should have no need for this additive.
Flour tortillas are usually made from white or whole wheat flour, water, salt, a source of fat, and, as standard in commercially made versions, baking powder. The dough is kneaded, allowed to rest, and then rolled out into a circle. Both sides are then briefly cooked on a hot griddle or, more typically with high production facilities, in a tortilla oven Like all soft flatbreads from throughout the world, common use for tortillas is as an accompaniment to meals to scoop up or wrap around foods. Extra large tortillas are produced that are used encase a variety of fillings, looking like a burrito. The fat in tortillas helps make them more pliable without cracking. Traditional tortilla-making depended on lard which, unlike vegetable shortening, provides similar baking properties without being hydrogenated. Made from rendered pork fat weighing in at 40% saturated fatty acids/58% unsaturated fatty acids, it has been a mainstay of TexMex cooking, not to mention an easily attainable fat for many throughout the world at least at one time or another. And yet, lard sold for home and commercial use is typically preserved with BHT.
Instead of lard, many tortillas are now made with hydrogenated vegetable shortening, products that definitely need to be avoided due to the accompanying presence of trans-fatty acids and its negative health implications. Products made with new non-hydrogenated shortenings based on palm fruit oil are emerging.
However, a less saturated fat choice would be the use of oil for the fat in flour tortillas. Look for brands that list the specific type of oil instead of the generic term "vegetable oil" whose quality and source is undetermined.
To keep tortillas more soft and shelf-stable, some are made with dough conditioners such as sodium stearoyl lactylate and L-cysteine, or preservatives and acidulants such as calcium propionate, sodium propionate, potassium sorbate, sorbic acid, and fumaric acid. Tortillas that are purchased fresh, used quickly, and stored properly have no need for these unnecessary additives.
Variations on the tortilla theme include flavored tortillas, such as sun-dried tomato or spinach, which are also colored to reflect the flavor. They should be made without artificial colors or artificial flavors, relying instead on vegetable purees (more typically, vegetable powders) or powdered spices added to the dough.
More significant innovations involve tortillas made with sprouted grain that has been ground into dough or dried into a flour. Not only does the sprouting process deactivate the mineral-binding phytic acid otherwise found in unleavened grain, it gives the tortillas a unique flavor that accentuates the grains. Also available are tortillas based on the Ezekiel 4:9 combination of sprouted grains and legumes.
Flour tortillas made with spelt or rice are good alternatives to the usual wheat-based versions.
Tortillas should be warmed up right before you're ready to eat them. There are several ways to make this happen. The quickest way is to heat them in a dry, ungreased skillet or electric griddle or on the grill over medium-high heat for 10-15 seconds. Flip and reheat for another 5–10 seconds and serve immediately or wrap them in clean dish towels or aluminum foil to keep them warm for a few minutes longer.
There's a reason that Mexican restaurants serve tortillas in a tortilla warmer. These are typically made from terra-cotta, ceramic, or a stone-like material formed into a round shape with a snug-fitting lid to keep in moisture and heat. The base of the warmer is first soaked in water to serve as the source of moisture. The tortillas are then put inside, topped with the tortilla warmer lid and then placed in the oven to warm. The tortilla warmer also serves to keep the tortillas warm at the table, up to 30 minutes.
If you don't have a tortilla warmer, you can improvise by wrapping the tortillas in aluminum foil and warming them in a 350-degree oven for 10 minutes. Or, faster yet, place tortillas in a vegetable steamer that is in a pot with a few inches of boiling water beneath.
Sprouted grain tortillas are best steamed briefly in a vegetable steamer or a tortilla warmer. Since sprouted grain flour is drier than flour ground directly from the grain, the extra moisture from steaming makes sprouted tortillas more flavorful, pliable, and digestible.